Field of the Invention
The present invention relates to improvements in an magneto-optical disc drive unit, and more particularly to an alarm device which is installed to a magneto-optical disc drive unit and informs that the drive unit is in an abnormally high temperature condition.
Description of the Prior Art
It is well known that a magneto-optical disc drive unit has been practically used to drive a magneto-optical disc to which various information is recorded and played back. Such a magneto-optical disc drive unit is schematically disclosed in FIG. 3. A spindle motor 12 is arranged to rotatingly drive a magneto-optical disc 13. An optical head 14 is disposed under the magneto-optical disc 13 and connected to a slide motor 15. The slide motor 15 is arranged to move the optical head 14 in the radial direction of the magneto:optical disc 13. A laser driver and signal reader 16 is connected to the optical head 14 to drive the optical head 14 and to record data signals to the magneto-optical disc 13 according to the control signals from an address decoder (no numeral), a modulator-demodulator (no numeral), a drive controller 7 and the like. The laser driver and signal reader 16 reads the data signals recorded in the magneto-optical disc 13 through the optical head 14 according to the control signals of the modulator-demodulator, the drive controller 7 and the like. A servo circuit 11 is connected to the slide motor 15 and drives the slide motor 15 in order to carry out the moving control of the optical head 14 in the radial direction of the magneto-optical disc 13 and a tracking. The servo circuit 11 further carries out the focus control of the optical head 14 and the rotation control of the spindle motor 12.
A bias magnet 8 is disposed above the magneto-optical disc 13, and generates an auxiliary magnetic field when data is recorded in the magneto-optical disc 13. A sensor 9 is connected to the drive controller 7 and disposed near the magneto-optical disc 13 in order to detect whether the magneto-optical disc 13 is in a loading condition or not. A load/unload driver 10 is connected to the drive controller 7 and carries out the loading and unloading of the magneto-optical disc 13.
However, the above discussed magneto-optical disc drive unit generates a lot of heat by the illumination of laser beam and the operation of the motor. Therefore, when an inner temperature of the drive unit 17 becomes higher than or equal to an allowable temperature such as 55.degree. C., it may cause a problem such that the drive unit 17 cannot normally operate. In order to prevent such a problem from causing, it has been proposed that a cooling fan for preventing the raising of the inner temperature is installed to the magneto-optical disc drive unit 17. Such a magneto-optical disc drive unit 17 with a cooling fan 18 is disclosed in FIGS. 4 and 5. The cooling fan 18 is attached to a back surface side of the drive unit 17. A control board 19, to which a controller and the like are installed, is disposed at a back surface side of the cooling fan 18. A dust filter 20 is detachably attached to the cooling fan 18. The dust filter 20 is installed at a side facing the control board 19 of the cooling fan 18. An operation lamp 4 is installed to the magneto-optical disc drive unit 17 in order to indicate that the magneto-optical disc drive unit 17 is in an operating condition.
If the permeability of the dust filter 20 is lowered due to the silting by dust, the cooling performance of the cooling fan 18 is degraded. Accordingly, in order to avoid the trouble due to such a silting, the dust filter 20 has been conventionally exchanged with new one at predetermined periods such as once per several months or once a year.
However, in case that the cooling fan 18 is broken down or the permeability of the dust filter 20 is unexpectedly rapidly lowered, the inner temperature of the unit may become higher than or equal to the allowable temperature. Accordingly, the magneto-optical disc drive unit 17 may malfunction or may be broken in such a condition.